The present invention relates generally to a cannula for temporary placement in a patient""s vascular system during surgery. More particularly, the invention relates to arterial and venous cannulas which can be employed to deliver blood from or to a bypass-oxygenator machine during cardiopulmonary bypass, or to deliver cardioplegia solution to the heart.
During various cardiothoracic surgeries, including cornary artery bypass grafting, heart valve replacement, septal defect repairs, and thoracic aortic aneurysm repair, cardiopulmonary bypass is often used to temporarily perform the function of the heart and lung while the surgeon repairs the diseased coronary artery, myocardium, valves, or aorta. Cardiopulmonary bypass is usually achieved by cannulation of the right atrium (where a venous return catheter carries deoxygenated blood from the right atrium to the bypass-oxygenator) and the aorta or femoral artery (where an arterial cannula returns the oxygenated blood from the bypass-oxygenator to the aorta).
Once cardiopulmany bypass is initiated, cardiac arrest is achieved by infusing cardioplegia solution into the coronary arteries to protect the myocardium and therefore reduce cardiac oxygen demand. Cardioplegia solution is often delivered through an aortic root cannula.
The cannulas that are currently available for arterial or venous cannulation, however, are cumbersome because of their rigid straight configuration, often interfering with the surgeon""s hands and instruments, slowing the operation. A need therefore exists for space-conserving cannula devices and methods which provide delivery of blood from or to a bypass-oxygenator machine and delivery of cardioplegia solution to the heart during cardiothoracic surgery.
The present invention provides a bendable shape-retaining cannula which accommodates arterial blood flow from a bypass-oxygenator machine, venous blood flow to a bypass-oxygenator machine, and/or delivers cardioplegia solution for cardiac arrest during cardiothoracic surgeries. More specifically, the invention provides a space-conserving cannula which is less prone to interfere with a surgeon""s field of operation.
In one embodiment, the bendable shape-retaining cannula comprises a tubular member having a proximal region adapted for attachment to a bypass-oxygenator machine, a distal region adapted to enter a blood vessel or heart chamber, a lumen extending therebetween, and a flexible region defined along a portion of the longitudinal axis. A suture flange is disposed about the cannula distal the flexible region and proximal the distal opening. The cannula is bendable because the flexible region comprises an accordion that can be bent by offsetting the proximal region relative to the distal region. Furthermore, the bend in the flexible region is retained until a positive force is applied to reorient the cannula. In certain embodiments, the cannula may also include an inner lining which either runs along its entire length or is limited to the flexible region so that blood or fluid flowing through the cannula does not encounter turbulance as it passes against the ridges of the flexible region. The inner lining thus provides smooth flow of blood or fluid through the cannula.
In another embodiment, the cannula may have a balloon occluder mounted on its distal region and communicating with a second lumen of the cannula. The balloon occluder provides aortic occlusion, thereby isolating the heart and the coronary blood vessels from the peripheral vascular system for cardiopulmonary bypass.
In another embodiment, the distal region of the cannula may have at least one venous drainage port. When the cannula is inserted in the right atrium, the superior vena cave, or the inferior vena cava, deoxgenated blood can be withdrawn through the lumen of the cannula to a bypass-oxygenator machine.
In still another embodiment, the cannula may have a filter as described in Barbut et al., U.S. Pat. No. 5,769,816, incorporated herein by reference, mounted on its distal region to entrap embolic material, such as thrombus, atheromatous plaque, fat, and tissue debris, from the aorta or cardiac chamber during cardiothoracic surgeries. The filter therefore reduces a patient""s risk of perioperative stroke.
The present invention also provides methods for cannulation of a body tissue, more particularly a patient""s blood vessel or heart chamber during cardiothoracic surgeries, including coronary artery bypass grafting, heart valve repair, septal defect repair, aneurysm repair, and correction of congenital defects. After an incision is made on a patient""s aorta, for example, the distal end of the bendable and shape-retaining cannula described above is introduced into the aorta such that part of the flexible region of the cannula remains outside of the aorta. Oxygenated blood from a bypass-oxygenator is delivered through the proximal end to the lumen of the cannula, and then to the aorta. The cannula is bent by offsetting its proximal region relative to the distal region, thus moving the proximal end of the cannula away from interfering with the surgeon. The cannula can be secured to the aorta by placing sutures between the suture flange and the aorta. The cannula may also be inserted in the aorta to deliver cardioplegia solution to the heart to achieve cardiac arrest. Similarly, the cannula can be inserted into the right atrium, the inferior vena cava, or the superior vena cava to carry deoxgenated blood through the venous drainage ports and the lumen of the cannula to a bypass-oxygenator machine.
The present invention therefore provides a cannula which is bendable and retains a bent conformation until a positive force is applied to change the conformation. The invention also provides methods for cannulating a blood vessel or heart chamber using a bendable cannula that can be adjusted to conserve space while operatively maintained within the blood vessel or heart.